The present invention relates to novel metal oxide clusters, ceramers made therefrom, and to the methods of making the same.
Polymer-ceramic composites or ceramers have the potential to combine the properties of polymers and ceramics, particularly oxides, in useful ways. Of special use are the so called nanocomposites which consist of alloys of polymers with ceramic particles of diameter much smaller than the wavelength of visible light. High refractive index, scratch and corrosion resistant optical coatings and radiation resistant coatings are such applications.
These inorganic/organic hybrid materials have been prepared by:
1) reacting an oligomer functionalized by a trialkoxysilane with a metal alkoxide and a water generating source in a single step to make a "ceramer"; PA0 2) prereacting an organofunctionalized (epoxy, alkenes, etc) trialkoxysilane with a metal alkoxide and a water generating source to generate an "ormocer" in the first step and then fusing these organocoated inorganic oxide clusters into a solid body by polymerization of the organic groups in the second step; PA0 3) swelling a metal alkoxide into a preformed elastomer and subsequently hydrolyzing the alkoxide to oxide; and PA0 4) preparation of a highly porous xerogel by hydrolysis of dilute metal alkoxides and subsequent infiltration and polymerization of monomer in the pores.
Methods 1, 2, 3 have so far been used only for thin film coatings since a large surface must be available, permitting small molecule condensation products to evaporate during alkoxide hydrolysis and self-condensation into the oxide. Method 2 is an extension of Method 1 since an oxide cluster is also surface functionalized by an organic functional group. However, in Method 2, the small molecule condensation products are completely removed from the cluster in a separate step prior to fabrication.
Recently the detailed structure of soluble alkoxide coated titanium oxide and trialkyl siloxane coated, hydroxy aluminum hydroxide ormocers have been elucidated. All useful ormocer materials are soluble in organic solvents and can be cast into films.
In an especially useful application of ormocer materials, oxide clusters coated with photopolymerizable groups have been fabricated into high refractive index, optical waveguides by photolithography.
In all applications so far the ormocers have been first solvated and solvent cast. In principal, compression molding of the organic coated clusters should be possible, thus opening the way for the manufacture of thick plaques which can now be made only by Method 4.
X-ray absorbing windows are presently manufactured from melt casting silica based glass of high PbO content or methylmethacrylate-methacrylic acid ionomers containing Pb.sup.+2 counterion. Although these absorbing windows are effective, the presence of lead makes them unsuitable for contained environments such as are present in space or undersea applications.